JPH11325905A - Vibration gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration gyro wherein external dimension of a sensor is small and a sensor chip is small. SOLUTION: A circular vibrator 110 supported, on a substrate, by counter support beams 112 is rotationally vibrated in electrostatic manner around a Z-axis vertical to the substrate with a drive electrode 113, and an angular speed around an X-axis orthogonal to the Z-axis is detected as a rotational vibration amount of the vibrator around a Y-axis through changes in electrostatic capacity between a detection electrode 116, on the substrate, and the vibrator 110. Here, a part of the vibrator 110 supported with a supporting beam 112 is a bottom part of a notch 111 formed from an outer periphery toward a center of a vibrator inside of outer-most diameter part, about the Z-axis of a part where the detection electrode and the vibrator overlap each other, while an electrode 115 which is driven allocated with a specified interval to the drive electrode is provided on the side, in radial direction, of the notch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrating gyroscope for measuring an angular velocity.

[0002]

2. Description of the Related Art Conventionally, an angular velocity sensor, that is, a gyro, is mounted on a ship or an aircraft and used as one of sensors for recording a navigation route thereof. It was expensive.

[0003] In recent years, the detection of angular velocity has been carried out by correcting the shaking of a recorded image due to camera shake of a video camera, recording the direction of travel of an automobile, and detecting the rotation of the body of an automobile using a signal obtained by detecting the rotation of the body of the automobile. It is becoming important to stabilize control. Detecting the angular velocity for video cameras and automobiles does not require high accuracy as in ships and aircraft, but requires miniaturization and cost reduction.

Conventionally used vibrating gyroscopes that detect angular velocity by detecting Coriolis force, such as a vibrating bar type, a tuning fork type, and a Sperry type, can be miniaturized and reduced in cost. The size is reduced to about several cm.

FIG. 5 is a diagram illustrating the principle of such a vibrating gyroscope. The vibrator 21 includes support springs 22a and 22b
The center axis 21a of the vibrator 21 is set to 2 by using a drive electrode 23 which is a piezoelectric element attached to one side of the vibrator 21.
The vibrator 21 is vibrated so as to be 1b and 21c. Here, in a state where the vibrator 21 is vibrated in the direction of the arrow 51, when an angular velocity in the direction of the arrow 52 is applied to the central axis 21a, a Coriolis force in the direction of the arrow 53 is generated. If the angular velocity is in the opposite direction, Coriolis force is generated in the opposite direction. The relationship among the Coriolis force F, the mass m and the velocity v of the vibrator 21, and the angular velocity Ω is F = mvΩ. If the angular velocity Ω is constant, the frequency of the Coriolis force naturally depends on the frequency of the vibrator 21. Matches. The displacement of the vibrator 21 due to the Coriolis force is detected by the detection electrode 25. The size of this structure is several cm to several tens cm.

In the above-described vibrating gyroscope, further miniaturization is considered difficult in manufacturing. Therefore, in order to further reduce the size, an example in which a micromachining technology is applied is being studied.
The following miniaturization has become possible.

FIG. 6 shows an example of a gyro using polysilicon as a structural material. A vibrator 31, support beams 32a and 32b, and an anchor 34 manufactured by micromachining technology.
a and 34b are assembled together to form the anchors 34a,
34b is fixed to the substrate 36 via a spacer,
The other is separated above the substrate 36. In such a configuration, the vibrator 31 is driven to vibrate in parallel with the substrate 36 by the electrostatic force of the comb-shaped drive electrodes 33a and 33b. At this time, when an angular velocity is given, the vibrator 31 is driven by Coriolis force.
Vibrates perpendicularly to the substrate 36. By the vibration,
The gap between the vibrator 31 and the substrate 36 changes, the capacitance between the vibrator 31 and a detection electrode (not shown) changes, and the angular velocity is measured.

On the other hand, FIG. 7 shows a configuration example of a gyro using polysilicon as a structural material in the same manner as in the above-described embodiment. In this embodiment, a rotation drive-rotation detection structure is employed. The disc-shaped vibrator 51 is supported by a four support beams 52 on the outside thereof with a predetermined gap between it and a substrate (not shown).
Are fixed to the substrate by anchors 54. The vibrator 51 is provided with four comb-shaped driven electrodes 55, and the comb-shaped driving electrodes 53a fixed to the substrate side.
53b and an appropriate gap. So 4
If a voltage is alternately applied to the two drive electrodes 53a and 53b,
The driven electrode 55 receives an electrostatic force, and the vibrator 51 rotationally vibrates around an A1 axis which is a rotation axis perpendicular to the substrate. At this time, the angular velocity Ω1 is set around the A2 axis, which is a rotation axis orthogonal to the A1 axis.
Is given, the vibrator 51 oscillates around an A3 axis, which is a rotation axis orthogonal to the A1 axis and the A2 axis, by the Coriolis force.
Angular velocity Ω1 can be identified by detecting the change in capacitance between 56b and vibrator 51.

[0009]

However, the vibration gyro having the rotation drive / rotation detection structure as shown in FIG. 7 has the following problems.

That is, in the vibrating gyroscope of the rotary drive-rotation detecting structure, the larger the diameter of the portion where the vibrator 51 and the detection electrodes 56a and 56b overlap to form the capacitance, that is, the larger the detection diameter Dd, the more the rotation around the detection axis relative to the angular velocity. And the change in capacity with respect to the amount of rotational vibration also increases. Therefore, in order to obtain a desired detection sensitivity, a sufficiently large detection diameter Dd is required, and the outer dimensions of the sensor must be correspondingly large.

However, in the conventional vibrating gyroscope having the rotary drive / rotation detecting structure, the support beam 52 supporting the vibrator 51, the driven electrode 55, and the drive electrodes 53a and 53b are arranged outside the circular vibrator 51. Therefore, the outer dimensions of the sensor are further increased by this amount, which is disadvantageous in reducing the size of the sensor chip.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vibration gyro having a rotary drive / rotation detecting structure which enables further miniaturization by focusing on such a conventional problem.

[0013]

According to a first aspect of the present invention, there is provided a vibrating gyroscope comprising a circular vibrator supported on a substrate by a predetermined gap with at least a pair of opposed supporting beams. The driving electrode electrostatically oscillates and vibrates about a first axis perpendicular to the substrate, and the angular velocity applied about a second axis orthogonal to the first axis is equal to the first and second angles of the vibrator. Vibration detected as a rotational vibration amount about a third axis orthogonal to the axis by a change in capacitance between the detection electrode provided at a position on the substrate facing the vibrator and the vibrator. In the gyro, a portion where the vibrator is supported by the support beam is set inside a portion where the detection electrode and the vibrator overlap with each other with respect to an outermost diameter portion with respect to the first axis. .

Further, the vibrating gyroscope according to claim 2 is
Furthermore, the drive electrode is set inside a portion where the detection electrode and the vibrator overlap with each other with respect to an outermost diameter portion with respect to the first axis.

Further, the vibrating gyroscope according to claim 3 is
Further, a reference electrode that is arranged with a predetermined gap with the vibrator and detects the amount of rotational vibration of the vibrator about the first axis as a change in capacitance between the vibrator and the reference electrode, A portion overlapping the vibrator is provided inside an outermost diameter portion with respect to the first axis.

The vibrating gyroscope according to claim 4 is
Further, an area of a portion where the detection electrode and the vibrator overlap each other is set to be constant even during rotational vibration of the vibrator around the first axis.

The vibration gyro according to claim 5 is
Further, the at least one pair of opposing support beams are two pairs of support beams whose opposing directions are orthogonal to each other, and the opposing directions form a predetermined angle with respect to the second axis and the third axis, and The electrode is provided along the second and third axes.

The vibrating gyroscope according to claim 6 is
In claim 5, the portion where the vibrator is supported by the support beam is the innermost portion of a notch formed from the outer periphery to the center of the circular vibrator, and the drive electrode and a predetermined portion are provided. A driven electrode disposed with a gap is provided on a radial side of the notch.

[0019]

FIG. 1 is a plan view of a vibrating gyroscope 100 according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a sectional view taken along the line III-III of FIG. It is sectional drawing which follows.

The vibrating gyroscope 100 includes a vibrator 110 having a circular basic shape, and comb-shaped driving electrodes 113a and 113b (four pairs in this example) arranged in a circumferential relationship in a pair.
The detection electrodes 116a and 116b (two pairs in this example) are configured as main parts.

The vibrator 110 has an appropriate gap between the vibrator 110 and the substrate 117, as will be described later, by means of two pairs of four opposing elastic support beams 112 in which the anchor portions 114 are fixed on the substrate 117. The center of the vibrator 110, and can rotate and vibrate around the Z axis as a first axis perpendicular to the substrate 117, and the X axis as a second axis orthogonal to the Z axis and Z
It is supported so as to be capable of rotational vibration around a Y axis as a third axis orthogonal to the axis and the X axis. As shown in FIG. 1, the support beam 112 is provided with two folded portions in the middle so that the support beam 112 has a substantial length longer than a length Ln, which affects the external dimensions of the sensor, and has low rigidity. .

The vibrator 110, the supporting beam 112, the anchor 114, and the driving electrodes 113a and 113b are, for example,
It can be formed on the substrate 117 by a surface micromachining technique including a sacrificial layer process using a conductive material such as polysilicon or plated metal.
Alternatively, single crystal silicon processed by etching or the like can be used as a constituent material. In addition, the detection electrode 11
Reference numerals 6a and 116b are conductive metal films such as aluminum or diffusion electrodes formed on the substrate 117, for example. When it is necessary to distinguish the detection electrodes for detecting the angular velocity Ω1 about the X axis and the angular velocity Ω2 about the Y axis, the detection electrodes 116ax and 116ax will be described below.
bx and the detection electrodes 116ay and 116by.

In the vibrating gyroscope 100 of the present embodiment,
A substantially equilateral trapezoidal notch 111 is formed from the outer periphery to the center of the circular vibrator 110, and this notch 111
Vibrator 110 supports beam 1 on top 111a of the innermost part of
12 is a portion supported by the same. Therefore, the support beam 112 is located substantially at the center of the notch 111 having a substantially trapezoidal shape. Also, the comb-shaped drive electrode 113
a, 113b while maintaining a predetermined gap, and comb-shaped driven electrodes 115a, 11 arranged so that the comb teeth mesh with each other.
5b is formed on the radial side 111b of the notch 111.

In this embodiment, the notch 111 is provided as described above, and the detection electrodes 116a and 116b are opposed to the vibrator 110 at a portion sandwiched by the notch 111.
Provided, the detection electrodes 116a and 116a
When the side of b (having a fan angle Θd) coincides with the side 111b of the notch 111, when the vibrator 110 rotationally vibrates, a part of the vibrator 110 detects the detection electrodes 116a and 116a.
As a result, the detection capacitance between the detection electrodes 116a and 116b protrudes from the portion b and fluctuates, resulting in noise. Therefore, in this example, the fan angle Θd formed by the sides of the detection electrodes 116a and 116b is changed to the side 1 of the adjacent cutout 111.
11b is smaller than the fan angle Θv formed by the detection electrode 116a,
The noise is prevented from protruding from the portion 116b.

Thus, the vibrating gyroscope 10 of the present embodiment
0, the supporting portion of the vibrator 110 by the supporting beam 112 (the diameter of this portion is referred to as the supporting diameter Ds) is the detection electrode 116
a, 116b and the transducer 110 are inside the detection diameter Dd, which is the outermost diameter of the detection capacitance portion where the transducer 110 overlaps. That is, if the outer diameter of the vibrator 110 is Dv, the support diameter Ds <
The detection diameter Dd <the transducer outer diameter Dv. In contrast, FIG.
In the conventional example shown in (1), support diameter Ds = vibrator outer diameter Dv> detection diameter Dd.

Next, the operation of the vibrating gyroscope 100 having the above configuration will be described.

Now, the comb-shaped driven electrode 1 of the vibrator 110
When a voltage is alternately applied to the four pairs of drive electrodes 113a and 113b so that a potential difference is generated between the drive electrodes 115a and 115b, electrostatic attraction acts on the driven electrodes 115a and 115b of the vibrator 110, and the vibrator 110 Oscillates about a Z axis which is a drive rotation axis perpendicular to the substrate 117. At this time, when the angular velocity Ω1 is applied around the X axis which is a rotation axis orthogonal to the Z axis, the vibrator 110 is rotated around the Y axis which is a detection axis orthogonal to the Z axis and the X axis by Coriolis force according to the angular velocity Ω1. Is rotationally vibrated, and this is electrically detected as a change in capacitance between the detection electrodes 116ay and 116by provided on the substrate 117, whereby the angular velocity Ω is obtained.
1 will be identified.

Also, as shown in FIG.
If similar detection electrodes 116ax and 116bx are provided at positions rotated by 90 degrees around the Z-axis with respect to ay and 116by, the angular velocity Ω2 around the Y-axis can be similarly detected and identified.

Further, the outside dimensions of the sensor (the opposing support beams 11)
In this embodiment, the length of the support beam which affects the distance between the outermost ends of the two anchors 114 is, as shown in FIG. The length Ln of the notch 111 up to the connection with the top side 111a, and in the conventional example, as shown in FIG. 7, the length from the connection with the anchor 54 to the connection with the outer periphery of the vibrator 51 Lo. Here, even if the length of the support beam is the same, as in the present invention, the smaller the support diameter Ds, the lower the rotational rigidity of the vibrator, so that the natural frequency decreases and the detection sensitivity increases. Therefore, if the same detection sensitivity as that of the conventional example is obtained, the length of the support beam can be shortened by reducing the support diameter Ds. That is, Ln <Lo
It can be. As a result, even if the outer diameter Dv of the transducer and the detection diameter Dd are equal in the present example and the conventional example, in this example, ｛(vibrator outer diameter Dv
−support diameter Ds) + 2 × (support beam Lo of the conventional example−support beam Ln of the present example) The sensor outer dimensions can be reduced by｝, contributing to miniaturization.

Here, in order to show the effect of reducing the external dimensions of the sensor according to the present invention, specific examples will be given.
The support diameter Ds is 1/3 of the transducer outer diameter Dv, the support beam length Ln in this example is 2/3 of the conventional support beam length Lo, and the conventional support beam length Lo and the transducer outer diameter are used. Assuming that Dv is equal, the outside dimensions of the sensor excluding the conventional anchor portion are:

[0031]

## EQU1 ## While Dv + 2Lo = 3Dv, the outside dimensions of the sensor excluding the anchor portion in this example are:

[0032]

Ds + 2Ln = (1/3) Dv + (4/3) D
v = (5/3) Dv. Therefore,

[0033]

## EQU3 ## (5/3) Dv / 3Dv = 5/9 That is, the outer dimension excluding the anchor portion is 5 compared to the conventional case.
/ 9.

FIG. 4 is a plan view showing a second embodiment of the present invention. The basic principle, configuration, and the like are the same as those in the first embodiment. However, in the present embodiment, the first embodiment has eight sets of drive electrodes 113a and 113
b and the driven electrodes 115a and 115b, but a part of them is not used for a driving purpose, but is used as a reference electrode for detecting a rotational vibration amount of the vibrator 110 by a change in capacitance between the electrodes. It was made. That is,
In FIG. 4, comb-shaped reference electrodes 1115a and 1115b are formed on one side of a notch 111 of a vibrator 110, a predetermined gap is maintained between them, and a comb is arranged such that the comb teeth mesh with each other. Toothed reference electrodes 1113a, 111
3b is provided. In this case, the driving force is half that of the first embodiment. However, by using the signal of the reference electrode as a feedback signal, the amount of rotational vibration of the vibrator 110 is controlled to be constant, and the sensor signal is stabilized. be able to.

In the above embodiment, two axes (X
An example of the vibrating gyroscope capable of detecting the angular velocity around the (axis, Y-axis) has been described.
116b may be a pair corresponding to a desired detection axis.

[0036]

As is apparent from the above description, according to the first aspect of the present invention, a circular vibrator supported by at least a pair of opposing support beams on a substrate with a predetermined gap is provided. The driving electrode electrostatically oscillates and vibrates around a first axis perpendicular to the first axis, and changes the angular velocity applied around a second axis perpendicular to the first axis to the first and second axes perpendicular to the vibrator. A vibration gyro that is detected by a change in capacitance between a detection electrode provided at a position on the substrate facing the vibrator and the vibrator as the amount of rotational vibration around the third axis; Since the portion where the vibrator is supported by the support beam is set inside the outermost diameter portion of the portion where the detection electrode and the vibrator overlap with respect to the first axis, the outer dimensions of the sensor are smaller than before. Can be reduced and the sensor A-flops can be reduced in size.

According to the second aspect of the present invention, the drive electrode is set inside the outermost diameter portion of the portion where the detection electrode and the vibrator overlap with respect to the first axis. In combination with the invention according to the first aspect, the external dimensions of the sensor can be reduced, and the sensor chip can be downsized.

According to the third aspect of the present invention, the first vibrator is disposed with a predetermined gap between the vibrator and the first vibrator.
A reference electrode that detects the amount of rotational vibration about an axis as a change in capacitance between the vibrator and the reference electrode, and the portion where the detection electrode and the vibrator overlap overlaps the outermost diameter portion with respect to the first axis. With the provision, the external dimensions of the sensor can be reduced in conjunction with the invention according to claim 1 or 2, the sensor chip can be downsized, and the sensor signal can be stabilized.

According to the fourth aspect of the present invention, the area of the overlapping portion between the detection electrode and the vibrator is made constant even during the rotational vibration of the vibrator around the first axis. In addition, noise can be reduced without changing the detection capacitance.

According to the fifth aspect of the present invention, the at least one pair of opposing support beams are two pairs of support beams whose opposing directions are orthogonal to each other, and the opposing directions correspond to the second axis and the third axis. On the other hand, since the detection electrodes form a predetermined angle and are provided along the second and third axes, they are symmetrical about the first axis and are relatively easy to manufacture.

According to the sixth aspect of the present invention, the portion where the vibrator is supported by the support beam is the deepest portion of the notch formed from the outer periphery to the center of the circular vibrator. In addition, since the driven electrode disposed with a predetermined gap from the driving electrode is provided on the radial side of the notch, the arrangement is excellent and the manufacture is relatively easy.

[Brief description of the drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a plan view of a second embodiment of the present invention.

FIG. 5 is a diagram illustrating the principle of a vibrating gyroscope.

FIG. 6 is a perspective view illustrating an example of a conventional vibrating gyroscope.

FIG. 7 is a plan view for explaining another example of a conventional vibrating gyroscope.

[Explanation of symbols]

 Reference Signs List 100 Vibrating gyroscope 110 Vibrator 112 Support beam 113a, 113b Drive electrode 114 Anchor 115a, 115b Driven electrode 116a, 116b Detection electrode 117 Substrate 1113a, 1113b Reference electrode 1115a, 1115b Reference electrode Ω1, Ω2 Angular velocity

Claims (6)

[Claims] A circular vibrator supported by at least a pair of opposing support beams with a predetermined gap on a substrate is electrostatically rotated and vibrated by a drive electrode about a first axis perpendicular to the substrate, An angular velocity applied around a second axis perpendicular to the first axis is defined as a rotational vibration amount of the vibrator about a third axis perpendicular to the first and second axes, and is applied to the vibrator on the substrate. In a vibrating gyroscope configured to detect by a change in capacitance between a detection electrode provided at an opposing position and the vibrator, a portion where the vibrator is supported by the support beam, the detection electrode and the A vibrating gyroscope wherein a portion where the vibrator overlaps is set inside an outermost diameter portion with respect to the first axis. 2. The vibration according to claim 1, wherein the drive electrode is set inside a portion where the detection electrode and the vibrator overlap with each other with respect to an outermost diameter portion with respect to the first axis. gyro. 3. A reference electrode which is arranged with a predetermined gap from the vibrator and detects a rotational vibration amount of the vibrator about the first axis as a change in capacitance between the vibrator and the vibrator. The vibrating gyroscope according to claim 1 or 2, wherein a portion where the detection electrode and the vibrator overlap is provided inside an outermost diameter portion with respect to the first axis. 4. The apparatus according to claim 1, wherein an area of a portion where the detection electrode and the vibrator overlap each other is constant even during rotational vibration of the vibrator around the first axis. 3. The vibrating gyroscope according to any one of 3. 5. The at least one pair of opposing support beams are two pairs of support beams whose opposing directions are orthogonal to each other, and the opposing directions form a predetermined angle with respect to the second axis and the third axis, and The vibrating gyroscope according to any one of claims 1 to 4, wherein the detection electrodes are provided along the second and third axes. 6. A portion where the vibrator is supported by the support beam is an innermost portion of a notch formed from an outer periphery to a center of the circular vibrator, and the drive electrode and a predetermined portion are provided. The vibrating gyroscope according to claim 5, wherein a driven electrode arranged with a gap is provided on a radial side of the notch.